R7350 - All DNS lookups are resolving to the router IP
I went to deploy a R7350 (AC2400) router the other day. With the factory settings, and WAN at DHCP, I was not getting anything on the Internet to resolve. The WAN is connected to a corporate network with open Internet and DHCP. The DHCP server on the corporate network was dishing out 220.127.116.11 as the primary (and only) DNS server.
If I hook up the cable going to the AC2400 WAN port directly to my laptop Ethernet port, I get an IP Address, and DNS server of 18.104.22.168 just fine, and Internet works just fine as it should.
Moving the cable to the AC2400 WAN port, and connecting the laptop to a LAN port on the AC2400, I get an IP Address of 192.168.1.xxx, and the DNS server is set to 192.168.1.1, as expected. But, no Internet connectivity worked.
When I did an nslookup of ANY domain name (google.com, bing.com, etc), every single domain was replying as having the IP address of 192.168.1.1. If I pring any domain name, I got replies but every reply came from 192.168.1.1. Interestingly, I could ping any Internet IP address such as 22.214.171.124 just fine. Also interesting, if I set my laptop IP address to 126.96.36.199 manually, it still did not work and I got the exact same results.
To be sure I wasn't having a DNS cache issue, I cleared it, and also tried access from my mobile phone AND another laptop, and the same symtoms resulted.
I updated the firmware to the latest version, which actually worked from the auto-update feature in the AC2400, so it seems the router itself either uses IP addresses, or it is able to resolve Internet interally just fine.
Frustrated, I swapped out the AC2400 with an AC2300 (7000P) that I had. I reset that unit to factory defaults and tried connectivity and everything worked 100% as expected. I compared the settings in both units and they were identical.
So, what is different between these two models and how do I fix it?